Idiopathic scoliosis is a condition in which the spine develops a curvature to the side. Its cause is unknown, and if untreated, it may progress to result in gross trunk deformity. It progresses chiefly at the onset of adolescence. Approximately ten percent of adolescents have some scoliosis, and approximately 0.2 percent are currently treated for it. Idiopathic scoliosis is defined in biomechanical terms, hence biomechanical studies of it are relevant. Research is proposed that is addressed to two main issues. The first is to gather basic biomechanical data on abilities of children with structurally normal spines and children with idiopathic scoliosis to control configurations of their spines. Evidence to date strongly suggests that idiopathic scoliosis progresses because of defects in the spine's posture control system, yet little is known about the system. The second issue is to explore biomechanical interactions between the spine and the rib cage. These may be involved in progression mechanics, and they clearly are involved in the trunk deformities that scoliosis causes and in the response of scoliosis patients to brace and surgical treatment. The understanding gained from these studies may be essential to discovering the etiology of idiopathic scoliosis, and it will help to improve treatment procedures.